Commell HS-870PZ, User Manual

Page: 49 / 52

HS-870PZ User’s Manual Appendix C
Watchdog Timer Programming Guide 49
LD8-CRF7- Bit[3..0] : Select IRQ resource for WDT time-out
( Setting of 2 selects SMI )
(3) WDT Programmimg guide
Step 1 . Enter extended function mode as mentioned as above.
Step 2 . Program WDT related CR.
(2-1) CR2B-b[4]P[0] ; Set pin output as WDT function
(2-2) CR07-P08h ; Point to LD8
(2-3) CRF6-Pxyh
; Program WDT time-out period and start
count down . xy = 00 ; No WDT time-out and counting
xy = 01 ; WDT time-out = 30 sec. and starts counting .
............
(2-4) Read CRF7-b4 if needed ; 0 : WDT counting
1 : WDT time-out happened
Step 3. Exit extended function mode as mentioned as above.
Example (ENABLE WDT AND SET WDT time-out = 5 minutes)
Step 1 .
MOV DX,2EH
MOV AL,87H
CLI ; disable interrupt
OUT DX,AL
JMP $+2
OUT DX,AL
STI ; enable interrupt
Step 2 .
MOV DX,2Eh
MOV AL,2BH
OUT DX,AL
MOV DX,2Fh
IN AL,DX ; READ CR2B
AND AL,0EFH
MOV AH,AL
MOV DX,2Eh
MOV AL,2BH
OUT DX,AL
MOV DX,2Fh
MOV AL,AH
OUT DX,AL ; CR2B-b[4]P[0]
MOV DX,2Eh
MOV AL,07H
OUT DX,AL ; point to Logical Device Number Register